Light emitting diode (LED) light bulbs can substantially increase residential and commercial energy efficiency if they achieve sufficient market adoption. However, commercially available designs are presently limited to 60 Watt-equivalent (We) luminosity. Market adoption is hindered by the lack of LED bulbs capable of replacing the common 75 W and 100 W incandescent bulbs to consumer satisfaction. Thermal management is a primary technology barrier to achieving higher luminosity in current LED bulb designs. State of the art approaches rely on heat sinks that remove heat only from the backside of the LED bulbs, so as not to interfere with the light output path on the front side. This constrains the heat rejection area to the region behind the LED, leading to high temperatures, lower efficiency, and shortened life.
A limiting factor in the widespread adoption of LED light bulbs has been the lack of units capable of replacing the most common 75 W and 100 W incandescent light bulbs. LED bulb designs in the incandescent replacement market today are limited to a maximum of 60 Watt-equivalent (We) operation, covering only the lower end of the potentially large retrofit market.
Thermal management is a primary technology barrier to achieving higher luminosity in LEDs. Maintaining the incandescent form factor supports mass adoption without requiring entirely new luminaires, and this forces the entire light source (including the driver electronics, LED chip(s), light diffuser, and heat sink) to be tightly packed into a small form factor. This small form factor leads to a challenging thermal management problem.
In a typical 11 to 12 W (electric) LED bulb with 60 We luminosity, about 15% (˜2 W) of the total electricity is wasted as heat in the driver electronics, and of the remaining 85% (˜10 W), at least half (˜5 to 6 W) is dissipated as heat in the LED chip itself. Inefficient rejection of all this heat through the limited surface area available on the backside of the bulb leads to overheating at operating levels beyond the 60 We available today.